Our research project is designed to provide information on the nature and control exerted by growth-controlling agents such as hormones (Thyroid hormone) on the developmental relationship between neuronal and/or non-neuronal structures in the emergence of coordinated behavior patterns. The trigeminal neck reflex with special reference to hand and mouth activity will be studied using rat fetuses and neonates as our experimental models. Developmental correlations between neuronal and non-neuronal peripheral structures which are involved in this behavior will be evaluated under a) normal and b) induced hypothyroid states in pregnant animals such that both maternal and fetal thyroids are inhibited. Quantitative analysis of nuclear centers in the brain in terms of neuronal number, cell size, cell loss, and differentiation of pre- and post-synaptic elements in the motor nucleus of V, mesencephalic nucleus of V, and anterior horn cells of C1-C4 in control group and experimental group of animals are now in progress.